The present invention relates to a can body having improved impact resistance by preliminarily coating an organic resin onto at least one side of the metal surface that becomes the inner surface of the can body and then forming the can by pressing, extruding and/or drawing. The coating of improved impact resistance and adhesiveness is provided by a polyester resin coating that is axially and planely oriented.
Conventional cans formed by pressing, extruding or drawing having a polyester resin coating internally adhered which coating has oriented molecules and obtained by applying a thermoplastic polyester film to a metallic material by thermal adhesion followed by drawing the coated metal structure are disclosed, for example, in Japanese Laid-open Patent No.60-172637 (1985). However, the cans described therein do not have sufficient impact resistance because of the problems which include dissolution of the can metal into the contents of the can and leakage of the can contents through holes caused by corrosion of the can metal. The metal base plate becomes directly contacted with the contents of the can due to cracks developed in the polyester organic resin coating that covers the inner surface of the can when subjected to shock during transportation or dropping of a packed carton after the content are filled into the can.
Thus, the need has arisen for a can that will not develop cracks in the polyester organic resin coating on the can inner surface even when the cans are subjected to shock during transportation or dropping of a packed carton.
The disclosure of the Japanese Laid-open Patent No. 60-172637 above proposes an inner coating that is oriented; namely, a polyester coating adhered on the inner surface of the can, wherein the oriented crystals have a C-axis axial orientation. However, it has become clear that such coating has a structure similar to that of fibrous structures and that the resin coating cracks in parallel with the C-axis when subjected to impact, if the normal line of the (100) plane of the axially oriented crystal along the C-axis of the coating on the can wall is oriented in a random direction. The impact resistance of the can will not be improved without overcoming this problem.